Coke drum discharge system

ABSTRACT

An apparatus including a coke drum for coking hydrocarbon substances, a valve disposed near the bottom of the coke drum, and a discharge conduit for removing coke from the coke drum, wherein the discharge conduit is connected to the valve such that when the valve is open, the coke may be removed via the discharge conduit.

[0001] This application claims benefit of provisional application No.60/331,156, filed Nov. 9, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a coke drum, and more particularly, toa discharge system for a coke drum.

BACKGROUND OF THE INVENTION

[0004] In a conventional delayed coking process, petroleum residues arefed at elevated temperatures to a large steel vessel called a coke drum,where the residues are thermally cracked and formed into coke. When thecoke drum has filled with coke, the drum is injected with steam andcooled with water. Subsequently, top and bottom covers of the drum areremoved in a process called unheading. Despite the open bottom of thedrum, however, the coke often remains inside the drum until it is cut.When cut, the coke falls out of the open bottom of the drum down a chuteor other conduit, so that it may be transported and further processed.

[0005] As discussed above, the conventional coking process requiresunheading the coke drum. Since the coke drum must contain a severeatmosphere of elevated temperatures, the bottom cover is typicallysecured to the coke drum by dozens of bolts, which often must beloosened manually. As a result, unheading is typically a labor intensivechore.

[0006] A further drawback of the conventional unheading process is thatit is difficult to use in the production of shot coke. Shot coke isunique because it will not always remain in the drum during and afterunheading. As a result, the coke will often pour out of the drum as thebottom cover is being removed. In addition, the shot coke may rest onthe bottom cover, putting a large load on the bottom cover and makingits controlled removal difficult.

[0007] Examples of apparatuses designed to mitigate the difficulties ofunheading the coke drum are shown in U.S. Pat. No. 2,318,131 toUtterback and U.S. Pat. No. 2,702,269 to Geller. Both Utterback andGeller disclose continuous processes that do not require unheading.

[0008] Utterback shows a spray coking process, in which spray-cokedmaterial is formed in chamber 1 and falls through a duct 2 into a vessel3, which contains oil. The solid, spray-coked material is suspended inthe oil, and the resultant mixture is pumped by a pump 6 into separators8 and 9, where screens collect the coke. Oil is pressured out of theseparators 8 and 9, and the collected coke is partially dried usingsteam. The coke then is removed through discharge piping 24, which isshown to contain a valve. The oil is returned to the vessel 3 via valvedpiping 11 or to an upstream tank 16 via valved piping 23.

[0009] Although Utterback mitigates the unheading problem, it alsosuffers from drawbacks. For example, rather than producingready-to-transport coke out of the coke drum 1, Utterback requiresadditional components (such as a vessel full of oil, a pump andseparators) to process the coke and get it ready for transport. Incontrast, a batch process produces coke that is ready for transportdirectly out of the coke drum.

[0010] Geller also discloses a continuous coking process. In Geller,feed material for coking is routed through pipe 2 into a coking space 1via a nozzle 3 directed vertically upwards. A casing 8 and lining 9surround the coking space 1 for indirect heating. The coke falls onto anoutlet branch 21 and is discharged from the bottom of the vessel using aworm 22, which is self-sealing against the passage of gas.

[0011] Although Geller's continuous process does not require unheading,it does suffer from at least two drawbacks. First, the coke leaving thedrum is at a high enough temperature that it may combust if it comesinto contact with air, so additional components are required to cool thecoke in an oxygen-depleted environment. Second, the coke drum needs anouter casing to heat its walls, implicating increased cost forinstallation and manufacture.

[0012] As the drawbacks of Utterback and Geller indicate, the continuousprocess for producing coke is not always desirable. Therefore, there isa need for an apparatus to discharge coke from a coke drum in batches,but without the drawback in conventional batch cokers of having tounhead the coke drum each time coke is removed.

SUMMARY OF THE INVENTION

[0013] This invention addresses the foregoing needs in the art byproviding a discharge conduit on a coke drum, the discharge conduithaving a ball valve. According to a preferred embodiment, cut coke canbe removed from the coke drum past the opened ball valve down thedischarge conduit, and a bottom cover of the coke drum does not need tobe unheaded.

[0014] In one aspect of the invention, an apparatus includes a coke drumfor coking, a valve disposed near the bottom of the coke drum, and adischarge conduit for removing coke from the coke drum. The dischargeconduit is connected to the valve such that when the valve is open, thecoke can be removed via the discharge conduit.

[0015] In another aspect the apparatus includes another valve disposedbeneath the valve, such that if the valve leaks, the other valvecontains the contents of the coke drum.

[0016] In yet another aspect of the invention, a steam supply isconnected to the valve at a higher pressure than exists upstream of thevalve.

[0017] In another aspect of the invention, the apparatus includes a sideconduit for feeding or draining the coke drum. Accordingly, when thevalve is closed, charge can be fed and water drained from the sideconduit.

[0018] In another aspect of the invention, the discharge conduit iscoupled to the valve which is coupled to the coke drum, such that no gapis formed between the bottom of the coke drum and a proximal end of thedischarge conduit.

[0019] In another aspect of the invention, a closed coke drum dischargesystem for removing coke from a coke drum includes a discharge conduitdisposed beneath the coke drum, and a ball valve interconnecting thedischarge conduit and the coke drum. The coke exiting the coke drum isenclosed until exiting the discharge conduit.

[0020] In yet another aspect of the invention, a discharge system for acoke drum includes a coke drum, a side conduit for feeding petroleum tothe coke drum, guiding means for guiding coke from the coke drum, andsealing means for sealing coke in the coke drum.

BRIEF DESCRIPTION OF THE DRAWING

[0021] The FIGURE is a side view of a preferred embodiment of adischarge system for a coke drum.

[0022] The FIGURE is a side view of a preferred embodiment of adischarge system for a coke drum.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] The FIGURE shows a discharge system 1 for a coke drum 2 whichreduces the frequency with which a bottom flange 3 of the coke drum 2needs to be unheaded. The discharge system 1 generally includes a ballvalve 6 and a discharge conduit 10.

[0024] The discharge system 1 may be used to coke hydrocarbon substancessuch as petroleum, for example. Included in the system is a side conduit4 for draining water from the coke drum 2, supplying steam or feeding apetroleum charge. The side conduit 4 is preferably connected to a funnel5, which itself is connected to the bottom of the coke drum 2. Thefunnel 5 may be permanently attached to the coke drum 2, bolted on, orremovably attached by hydraulic means as disclosed in U.S. Pat. No.6,223,925 to Malsbury, for example.

[0025] Below the side conduit 4 and funnel 5 is a ball valve 6,preferably having a steam supply 8 connected to it. The ball valve 6 ispreferably a conventional, double-seat, full-port ball valve. Although aball valve is illustrated, other types of valves may be used withoutdeparting from the scope of the invention.

[0026] The steam supply 8 connected to the ball valve 6 preferablysupplies steam at a higher pressure than that found upstream of the ballvalve 6, so that if the ball valve 6 seat leaks, it will fail safe. Inthis way, steam will be injected into the coke drum 2 should the ballvalve 6 leak, and the high-pressure contents of the coke drum 2 will notbe jetted into the environment. An arrangement for providing a steamsupply to a ball valve is shown in U.S. Pat. No. 5,417,811 to Malsbury,incorporated herein by reference.

[0027] Beneath the ball valve 6 is a discharge conduit 10, preferablyhaving a mitered section 12. Of course, one of ordinary skillunderstands that while no mitered section is necessary, it may beconvenient depending on the location of the coke drum 2 and thedischarge cart (not shown), which collects the coke and transports it.Regardless, the discharge conduit 10 may be an open chute,large-diameter pipe or any other conduit suitable for conveying coke.Preferably, the discharge conduit 10 is the large-diameter pipe.

[0028] The mitered section 12 is preferably overlaid, as is known in theart, with a welding material. The overlay resists erosion at the bendand adds life to the discharge conduit 10.

[0029] As can be seen in the drawing, there is no gap from the bottom ofthe coke drum 2 to the proximal end of the discharge conduit 10. Thisarrangement allows the discharge system 1 to be used in the productionof shot coke, for example, as there is no danger that the coke mightpour out of a partially open cover. Of course, a gap may be formed inthe discharge system 1 if it is convenient, but unlike conventionalsystems (where a gap is necessary to permit unheading), it is notnecessary.

[0030] The discharge system 1 preferably includes a second valve 14. Thesecond valve 14 contains the contents of the coke drum 2 if the ballvalve 6 should fail. The second valve 14 may be of any suitableconstruction, including a gate valve, a slide gate or an auto-blindingstation.

[0031] The operation of the ball valve 6 and second valve 14 may beautomated. Included in the automation control is an interlock whichprevents inadvertent opening or closing of the ball valve 6 or thesecond valve 14.

[0032] A possible operation of the coke discharge system 1 is asfollows. While the ball valve 6 is closed, the coke drum 2 is fed withcharge, such as petroleum, through side conduit 4. When the coke drum 2is full, charging is stopped and steam is injected via side conduit 4 inorder to remove valuable vapors from the coke drum 2. Once the vaporshave been removed, water is introduced to the coke drum 2 through theside conduit 4 in a quenching step until the water has reached to thetop of the coke drum 2. Subsequently, the ball valve 6 and second valve14 (if present) are opened, draining the quench water, and the coke inthe coke drum 2 is cut with a high-pressure water cutter, such as thetype disclosed in U.S. Pat. No. 5,417,811 to Malsbury. The cut cokefalls off the interior walls of the coke drum 2, and the coke and waterfrom the cutter fall through the funnel 5 and out the discharge conduit10. From there the coke is collected and transported.

[0033] As is apparent from the above disclosure, the present inventionhas the advantage of not requiring unheading every time coke is removedfrom the drum. Instead, a single ball valve is opened, allowing the coketo fall down the discharge conduit. In addition, the apparatus may beconstructed without a gap between the bottom of the coke drum and thedischarge conduit. Such an arrangement allows the apparatus to be usedin the production of shot coke.

[0034] While the present invention has been described with respect towhat is at present considered to be the preferred embodiments, it shouldbe understood that the invention is not limited to the disclosedembodiments. To the contrary, as exemplified above, the invention isintended to cover various modifications and equivalent arrangementsincluded within the spirit and scope of the appended claims. Therefore,the scope of the following claims is intended to be accorded thebroadest reasonable interpretation so as to encompass all suchmodifications and equivalent structures and functions.

1-17. (Cancelled)
 18. A process for repetitively producing and removingcoke from a delayed coker vessel, wherein the coker vessel has a bottomportion defining an aperture through which coke is released, comprising:(a) sealing an aperture closure housing to the bottom portion of thecoker vessel; (b) moving a closure member within the closure housing toclose the aperture; (c) feeding a heavy hydrocarbon feed into the cokervessel through a feed line attached to the coker vessel; (d) coking theheavy hydrocarbon in the coker vessel; (e) moving the closure memberwithin the closure housing to open the aperture to allow coke removalfrom the coker vessel; (f) releasing coke through the aperture; and (g)repeating steps c through f successively.
 19. The process of claim 18wherein step (c) further comprises attaching the feed line at a sideentry position.
 20. The process of claim 18, wherein step (a) furthercomprises sealing a funnel to the coker vessel bottom and attaching thefeed line to the funnel at a side entry position.
 21. The process ofclaim 18 wherein step (a) further comprises forming a seal between theaperture closure housing and the bottom portion of the vessel whereinthe seal withstands pressures within the vessel within operatingpressures.
 22. The process of claim 21 wherein step (a) furthercomprises forming a seal between the aperture closure housing and thebottom portion of the vessel wherein the seal withstands vesseltemperatures through repetitive coking/decoking cycles within operatingranges.
 23. The process of claim 18, wherein step (a) further comprisessealing a coke chute to a bottom portion of the aperture closurehousing.
 24. The process of claim 18 wherein step (a) further comprisesplacing a gasket between the bottom portion of the vessel and closureunit and pressure-tightly joining the vessel bottom, the gasket and theclosure unit.
 25. The process of claim 19, wherein step (a) furthercomprises placing a gasket between the bottom of the closure unit andthe coke chute and pressure-tightly joining the closure unit, thegasket, and the coke chute.
 26. The process of claim 24 wherein thegasket comprises an annular corrugated metal bonded to a graphitematerial.
 27. The process of claim 25 wherein the gasket comprises anannular corrugated metal bonded to a graphite material.
 28. A process inaccordance with claim 23, wherein the process further comprises usingthe chute to assist in directing coke removed from the coker vessel. 29.A process in accordance with claim 18 wherein steps (b) and (e) furthercomprise moving the closure member automatically.
 30. The process ofclaim 29 wherein the automatic movement of the closure member isremotely controlled.
 31. A process in accordance with claim 18 whereinthe coking step (d) is carried out within an operating temperaturerange, the opening step (e) is done at another operating temperaturerange, and the valve is selected to withstand repeated operation attemperatures cycling between step (d) and step (e).
 32. A process inaccordance with claim 18, wherein the closure member of steps (b) and(e) is a valve.
 33. A process in accordance with claim 32, wherein thevalve is selected from a gate valve, a ball valve, a slide valve, aknife valve or a wedge plug valve.
 34. A process in accordance withclaim 18 wherein the aperture opens to a specified diameter.
 35. Aprocess in accordance with claim 18 wherein the closure housing andclosure member are mounted together.
 36. The process of claim 35 whereinthe closure unit is removable from the coker vessel.
 37. A coker vesselcomprising: (a) a vessel having a side aperture and a flanged bottomaperture; (b) a feed pipe fitted to said side aperture; (c) an apertureclosure unit fitted and sealed to said bottom aperture; (d) a closuremember moveable within said closure unit; and (e) a coke chute sealed tothe bottom portion of said closure unit for directing coke from thevessel.
 38. The coker vessel of claim 37 wherein the closure membercomprises a valve.
 39. The coker vessel of claim 38, wherein the valveis a gate valve, a ball valve, a slide valve, a knife valve or a wedgeplug valve.
 40. The coker vessel of claim 38 wherein the valve furthercomprises an automatic valve.
 41. The coker vessel of claim 38 whereinthe bottom aperture has a specified opening.